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Impact data

>Are you suggesting, then, that an object puncturing the crust of the earth
>leaving a 120 mile wide gaping hole straight to the mantle turning the ocean
>above into a boiling cauldren, raining glowing ash and molten rock on all
>parts of the globe igniting fires everywhere would not leave prominent
>residue in the geological record?

Check out the appropriate stratigraphic data.  The Chixculub impact only
goes down into mid-Cretaceous anhydrite deposits, not "straight to the
mantle" at all.  The bottom of the crater was found long before they
recognized it as a crater.

The evidence for global fires is VERY weak - sure, ash is found at the K-T
boundary, but ash is found in just about every cm of strata in the
terrestrial environment.

>If you find iridium and ash deposits
>widespread across the earth that hint of being contemporary to the Yucatan
>crater it is highly likely that these deposits belong to the impact, since
>iridium and ash had to have fallen all over the earth in copious amounts from
>the impact.

If they are contemporary with Chixculub, then that is a reasonable
conclusion.  If Chixculub is mid-Campanian, than the iridium and shocked
quartz we've seen are from a different impact (and, probably, there would
be iridium and shocked quartz in the early late Campanian).

>And this very layer coincides with the extinction of the
>dinosaurs, adding further evidence that the impact occurred at this time.

Evidence of impact does not equal evidence of extinction.
Evidence of extinction does not equal evidence of impat.
Coincidence of impact and extinction (strongly) suggests a causal link.

> Yes, I know you are irritated that I keep referring to the extinction event
>as a way to pin down the date of the strike since you believe that I am
>trying to prove that the strike was cause of the extinction.  That is not
>what I am trying to do.  You have mentioned that the strike may have occurred
>8 million years before the KT boundary, and I am saying that it is absolutely
>impossible for an event like the one that formed Chixculub crater to have
>occurred without a severe effect to all life on earth.

We don't know that.  All we have are models scaled up from much smaller
explosions.  As you yourself implied, the Chixculub impactor would have
penetrated the mantle.  However, that hypthosis fails the text, since the
bottom of the crater is known to lie far above the bottom of the crust.

[Similarly, Kelvin's equations proved the Earth was only a few tens of
millions of years old.  Sedimentological evidence showed that was wrong,
and later discoveries (radioactive decay) provided a means of bring physics
up to speed with geology.]

I would agree that the impact would LIKELY have caused mass death.
However, the hypothesis hasn't been tested.

>The Indian lava plains were not formed in a brief period of time, and would
>not have left the sharp iridium spike that is seen in so many places.  Also,
>their is little evidence supporting that this vulcanism had deleterious
>effects on the fauna globally during the span of its activity.

No less evidence for the global effects of mass vulcanism than the
hypothesis that large bolide impacts might cause global extinctions.

Thomas R. Holtz, Jr.                                   
Vertebrate Paleontologist in Exile                  Phone:      703-648-5280
U.S. Geological Survey                                FAX:      703-648-5420
Branch of Paleontology & Stratigraphy
MS 970 National Center
Reston, VA  22092